1. Field of the Invention
The invention relates to a method of wideband intercorrelation and to a device implementing this method.
It can be applied notably to any system such as a system enabling wideband electrical signals to be put into correlation.
2. Description of the Prior Art
In a known way of carrying out such a correlation, signals R(t) and S(t) to be correlated are applied to the two ends of a delay line comprising N coupling points (typically N=128) that are evenly spaced out (FIG. 1). The spacing between two adjacent points corresponds to a time .tau. of propagation of the signal S(t). Thus at each of these points, with an index p, it is possible to pick up a fraction of the signal S(t-p.tau.) +R[t-(N-p).tau.]. Each coupling point is followed by a diode that raises the signal to the second power. A passband filter then enables the isolation, at each output, of the product S(t-p.tau.) R[t-(N-p).tau.] which is then integrated. The signals S(t) and R(t) may then have an instantaneous band that can cover a 20 GHz band. A band such as this calls for a sampling such that .tau. is equal to about 12.5 ps. At present, the number of increments limited to N=128 enables only one correlation on 1.6 ns, to the detriment of an efficient determination of the frequencies contained in the signal.
The method and device of the invention enable operation with a fineness of increments permitting a 20 GHz passband, it being possible to take the number of these increments to N=1 024 or 2 048. This embodiment uses an optical architecture based on 2D spatial light modulators.